Remote sonic location system

Abstract

A hydrophone (16) having a short-baseline array of transducers (12A, 12B, and 12C) as well as a long-baseline array of transducers (14A, 14B, and 14C) includes switches 30A, 30B, and 30C) for selectively connecting the outputs of the arrays to a cable (18) that carries the signals to processing circuitry (20) aboard an ocean-going vessel (24). The switches (30A, 30B and 30C) change state in accordance with the output of a narrow-band filter (42), which indicates whether the received signal is of a predetermined frequency and thus is likely to have been produced by an intended source. Due to the delay inherent in the narrow-band filter 42, the processing circuitry (20) thus processes the response of the long-baseline array to the first part of a beacon pulse and the response of the short-baseline array to the second part of the beacon pulse.

What is claimed as new and desired to be secured by Letters Patent of the United States is: 
     
       1. In a sonic location system comprising a remote unit for sensing pulsed sonic signals and producing therefrom processing-unit input signals from which a direction of a source of the sonic signals can be deduced, a processing unit for processing the processing-unit input signals to generate a display that indicates the direction of the sonic signal source, and a cable connected between the remote unit and the processing unit for carrying the processing-unit input signals from the remote unit to the processing unit, the sonic location system comprising: A. a long-baseline transducer array and a short-baseline transducer array, each array being located in the remote unit and comprising a plurality of sonic transducers for receiving the sonic signals and for producing electrical transducer signals in response to received sonic signals, at least a pair of the transducers of the long-baseline array being spaced apart by a first, relatively long distance to resolve the direction of the sonic signal source, and at least a pair of the transducers of the short-baseline array being spaced apart by a second, relatively short distance to resolve angular ambiguities in the long-baseline array;   B. signal-detection means for generating a switch-state signal whose value depends on whether the first portion of a single pulse being received by the transducer arrays is of a predetermined type;   C. interruptible long-baseline and short-baseline signal channels located in the remote unit for receiving the transducer signals from the long- and short-baseline arrays, respectively, each signal channel processing its respective received transducer signals to produce respective channel signals, and each signal channel applying its respective channel signals to the cable as the processing-unit input signals when that signal channel is completed but not when that signal channel is interrupted; and   D. switching means, responsive to the switch-state signal, for selectively assuming first and second switch states and being interposed in the long-baseline and short-baseline signal channels, and to (i) in the first switch state, complete a first one of the long- and short-baseline signal channels and interrupt a second one thereof and (ii) in the second switch state, complete the second signal channel and interrupt the first signal channel, the switching means being responsive to the switch-state signal to assume one of the first or second switch states in accordance with the value of the switch-state signal.   
     
     
       2. The location system of claim 1 wherein the signal-detection means is located in the processing unit. 
     
     
       3. Apparatus as in claim 1 wherein the element spacing of the large-baseline array is greater than one wavelength of the received sonic signals. 
     
     
       4. Apparatus as in claim 1 wherein the element spacing of the short-baseline array is less than one wavelength of the received sonic signals. 
     
     
       5. In a sonic location system comprising a remote unit for sensing sonic signals and producing therefrom processing-unit input signals from which a direction of a source of the sonic signals can be deduced, a processing unit for processing the processing-unit input signals to generate a display that indicates the direction of the sonic signal source, and a cable connected between the remote unit and the processing unit for carrying the processing-unit input signals from the remote unit to the processing unit, the sonic location system comprising: A. a long-baseline transducer array and a short-baseline transducer array, each array being located in the remote unit and comprising a plurality of sonic transducers for receiving the sonic signals and for producing electrical transducer signals in response to received sonic signals, at least a pair of the transducers of the long-baseline array being spaced apart by a first, relatively long distance to resolve the direction of the sonic signal source, and at least a pair of the transducers of the short-baseline array being spaced apart by a second, relatively short distance to resolve angular ambiguities in the long-baseline array;   B. signal-detection means for generating a switch-state signal whose value depends on whether signals received by the transducer arrays are of a predetermined type, including: i. a bandpass filter, connected to receive one of the processing-unit input signals, for producing a band-limited filter output therefrom;   ii. threshold means, connected to receive the band-limited filter output, for generating as the switch-state signal a signal having one value when the band-limited filter output exceeds a predetermined threshold and another value when the band-limited filter output does not exceed the predetermined threshold.     C. interruptible long-baseline and short-baseline signal channels located in the remote unit for receiving the transducer signals from the long- and short-baseline arrays, respectively, each signal channel processing its respective received transducer signals to produce respective channel signals, and each signal channel applying its respective channel signals to the cable as the processing-unit input signals when that signal channel is completed but not when that signal channel is interrupted; and   D. switching means, responsive to the switch-state signal, for selectively assuming first and second switch states and being interposed in the long-baseline and short-baseline signal channels, and to (i) in the first switch state, complete a first one of the long- and short-baseline signal channels and interrupt a second one thereof and (ii) in the second switch state, complete the second signal channel and interrupt the first signal channel, the switching means being responsive to the switch-state signal to assume one of the first or second switch states in accordance with the value of the switch-state signal.   
     
     
       6. The location system of claim 5 wherein the processing unit comprises: A. memory means, responsive to the processing-unit input signals, for maintaining as contents a record of the processing-unit input signals that were most recently received; and   B. bearing-determination means, responsive to the band-limited filter output and the memory means, for determining the bearing of the source of the sonic signals by processing, as the output of the first signal channel, the contents of the memory means received at the time when the threshold means determined that the band-limited filter output reached the predetermined threshold, and then processing subsequently received contents of the memory means as the output of the second signal channel.   
     
     
       7. In a sonic location system comprising a remote unit for sensing sonic signals and producing therefrom processing-unit input signals from which a direction of a source of the sonic signals can be deduced, a processing unit for processing the processing-unit input signals to generate a display that indicates the direction of the sonic signal source, and a cable connected between the remote unit and the processing unit for carrying the processing-unit input signals from the remote unit to the processing unit, the sonic location system comprising: A. a long-baseline transducer array and a short-baseline transducer array, each array being located in the remote unit and comprising a plurality of sonic transducers for receiving the sonic signals and for producing electrical transducer signals in response to received sonic signals, at least a pair of the transducers of the long-baseline array being spaced apart by a first, relatively long distance to resolve the direction of the sonic signal source, and at least a pair of the transducers of the short-baseline array being spaced apart by a second, relatively short distance to resolve angular ambiguities in the long-baseline array;   B. signal-detection means for generating a switch-state signal whose value depends on whether signals received by the transducer arrays are of a predetermined type;   C. interruptible long-baseline and short-baseline signal channels located in the remote unit for receiving the transducer signals from the long- and short-baseline arrays, respectively, each signal channel processing its respective received transducer signals to produce respective channel signals, and each signal channel applying its respective channel signals to the cable as the processing-unit input signals when that signal channel is completed but not when that signal channel is interrupted;   D. switching means, responsive to the switch-state signal, for selectively assuming first and second switch states and being interposed in the long-baseline and short-baseline signal channels, and to (i) in the first switch state, complete a first one of the long- and short-baseline signal channels and interrupt a second one thereof and (ii) in the second switch state, complete the second signal channel and interrupt the first signal channel, the switching means being responsive to the switch-state signal to assume one of the first or second switch states in accordance with the value of the switch-state signal. wherein the processing unit comprises:   E. memory means, responsive to the processing-unit input signals, for maintaining as contents a record of the processing-unit input signals that were most recently received; and   F. bearing-determination means, responsive to the band-limited filter output and the memory means, for determining the bearing of the source of the sonic signals by processing, as the output of the first signal channel, the contents of the memory means received at the time when the threshold means determined that the band-limited filter output reached the predetermined threshold, and then processing subsequently received contents of the memory means as the output of the second signal channel.   
     
     
       8. A sonic location system comprising: A. a long-baseline transducer array and a short-baseline transducer array, each array being located in the remote unit and comprising a plurality of sonic transducers for receiving pulsed sonic signals and for producing electrical transducer signals in response to received sonic signals, at least a pair of the transducers of the long-baseline array being spaced apart by a first, relatively long distance to resolve the direction of the sonic signal source, and at least a pair of the transducers of the short-baseline array being spaced apart by a second, relatively short distance to resolve angular ambiguities in the long-baseline array;   B. signal-detection means for generating a switch-state signal whose value depends on whether the first portion of a single pulse received by the transducer arrays is of a predetermined type;   C. interruptible long-baseline and short-baseline signal channels located in the remote unit for receiving the transducer signals from the long- and short-baseline arrays, respectively, each signal channel processing its respective received transducer signals to produce respective channel signals, and each signal channel applying its respective channel signals to the cable as the processing-unit input signals when that signal channel is completed but not when that signal channel is interrupted; and   D. switching means, responsive to the switch-state signal, for selectively assuming first and second switch states and being interposed in the long-baseline and short-baseline signal channels, and to (i) in the first switch state, complete a first one of the long- and short-baseline signal channels and interrupt a second one thereof and (ii) in the second switch state, complete the second signal channel and interrupt the first signal channel, the switching means being responsive to the switch-state signal to assume one of the first or second switch states in accordance with the value of the switch-state signal.   
     
     
       9. Apparatus as in claim 8 wherein the element spacing of the large-baseline array is greater than one wavelength of the received sonic signals. 
     
     
       10. Apparatus as in claim 8 wherein the element spacing of the short-baseline array is less than one wavelength of the received sonic signals. 
     
     
       11. A sonic location system comprising: A. a long-baseline transducer array and a short-baseline transducer array, each array being located in the remote unit and comprising a plurality of sonic transducers for receiving the sonic signals and for producing electrical transducer signals in response to received sonic signals, at least a pair of the transducers of the long-baseline array being spaced apart by a first, relatively long distance sufficient to resolve the direction of the sonic signal source, and at least a pair of the transducers of the short-baseline array being spaced apart by a second, relatively short distance sufficient to resolve angular ambiguities in the long-baseline array;   B. signal-detection means for generating a switch-state signal whose value depends on whether the signals received by the transducer arrays are of a predetermined type, including: i. a bandpass filter, connected to receive one of the processing-unit input signals, for producing a band-limited filter output therefrom;   ii. threshold means, connected to receive the band-limited filter output, for generating as the switch-state signal a signal having one value when the band-limited filter output exceeds a predetermined threshold and another value when the band-limited filter output does not exceed the predetermined threshold;     C. interruptible long-baseline and short-baseline signal channels located in the remote unit for receiving the transducer signals from the long- and short-baseline arrays, respectively, each signal channel processing its respective received transducer signals to produce respective channel signals, and each signal channel applying its respective channel signals to the cable as the processing-unit input signals when that signal channel is completed but not when that signal channel is interrupted; and   D. switching means, responsive to the switch-state signal, for selectively assuming first and second switch states and being interposed in the long-baseline and short-baseline signal channels, and to (i) in the first switch state, complete a first one of the long- and short-baseline signal channels and interrupt a second one thereof and (ii) in the second switch state, complete the second signal channel and interrupt the first signal channel, the switching means being responsive to the switch-state signal to assume one of the first or second switch states in accordance with the value of the switch-state signal.   
     
     
       12. The sonic location system of claim 11 wherein the processing unit comprises: A. memory means, responsive to the processing-unit input signals, for maintaining as contents a record of the processing-unit input signals that were most recently received; and   B. bearing-determination means, responsive to the band-limited filter output and the memory means, for determining the bearing of the source of the sonic signals by processing, as the output of the first signal channel, the contents of the memory means received at the time when the threshold means determined that the band-limited filter output reached the predetermined threshold, and then processing subsequently received contents of the memory means as the output of the second signal channel.   
     
     
       13. The location system of claim 8 wherein the processing unit comprises: A. memory means, responsive to the processing-unit input signals, for maintaining as contents a record of the processing-unit input signals that were most recently received; and   B. bearing-determination means, responsive to the band-limited filter output and the memory means, for determining the bearing of the source of the sonic signals by processing, as the output of the first signal channel, the contents of the memory means received at the time when the threshold means determined that the band-limited filter output reached the predetermined threshold, and then processing subsequently received contents of the memory means as the output of the second signal channel.   
     
     
       14. A location system for determining the bearing of a pulsed signal source, the location system comprising: A. a first array of transducers, with at least a pair of transducers spaced apart by a distance to resolve the bearing of the signal source, to thereby form a long-baseline array;   B. a second array of transducers, with at least a pair of the transducers spaced part by a distance to resolve ambiguities inherent in the long-baseline array, to thereby form a short-baseline array;   C. detection means, for determining if the first portion of a pulse output from the long-baseline array is a signal of a proper predetermined type;   D. means for processing the long- and short-baseline array outputs, by operating on the output of the long-baseline array output until such time as the detection means determines that the first portion of the long-baseline array output is of the proper predetermined type, and then afterwards operating on the short-baseline array output.